Are you actually running your 5960X at 3.0 GHz? If so, the first 'upgrade' I would recommend for your build is to overclock your CPU. Nearly everything else you listed would have negligible benefit.
PCDesignerR :
Looking to improve upon the current build I could:
Upgrade to only using M2 drives for storage
Upgrade the closed loop liquid cooler to something a bit newer/bigger/better
Upgrade to an AX1500i
Upgrade to a GTX 1080 (as soon as available)
Upgrade to Corsair Dominator 3000 MHz
Upgrade my motherboard to a more solid X99 board (I know there are nicer X99 boards than mine available)
BIG QUESTION: Price not being a factor, if you could use ANY X99 motherboard, what would you hands down say that the best damn X99 board on the market would be by any measure of anything?
1) Assuming you already have your OS and apps on an M.2 drive, this would provide little to no advantage
2) Unless you're overclocking heavily and being held back by high temps, this would be pointless
3) Pointless. Your current PSU is plenty even if you were to add another Titan
4) Probably the only thing in this list that would provide a reasonable performance boost
5) Would provide negligible benefit anywhere except for a handful of very specific use cases/applications
6) Is there something wrong with your current mobo? Is it missing something you want? Unless there's some specific feature that another mobo has that yours doesn't, I can't see how upgrading would improve performance in any way.
Regarding Z170:
First off, the Z170A is a specific Asus mobo. The chipset is simply Z170. Secondly, moving to a Z170 platform would be a downgrade, or a sideways move at best.